import java.util.Stack;

class MyQueue {
    private Stack<Integer> stack1;
    private Stack<Integer> stack2;

    public MyQueue() {
        stack1=new Stack<>();
        stack2=new Stack<>();
    }
    
    public void push(int x) {
        stack1.push(x);
    }
    
    public int pop() {
        if(empty()){
            return -1;
        }
        else{
            if(stack2.empty()){
                while(!stack1.empty()){
                    int tmp=stack1.pop();
                    stack2.push(tmp);
                }
                return stack2.pop();
            }
            else {
                return stack2.pop();
            }
        }
    }

    
    public int peek() {
        if(empty()){
            return -1;
        }
        if(!stack2.empty()){
            while(!stack1.empty()){
                int tmp=stack1.pop();
                stack2.push(tmp);
            }
        }

        return stack2.peek();

    }
    
    public boolean empty() {
        return stack2.empty()&&stack1.empty();
    }
}